Is it possible to be infected again with a virus, bacteria or even a parasite, shortly after having tested positive for the first time, then having recovered from it and being supposed to be protected by antibodies or immune cells? This is a question – raised in recent weeks by the case of dozens of South Korean patients cured and then tested positive for Sars-CoV-2 again – which seems to have been settled following the publication of a WHO opinion.
→ LIVE. Coronavirus: May 8 ceremonies in a format limited to three days of deconfinement
An in-depth study of the different cases in question indicates that you cannot be infected twice in a row. ” It is not contagious. It is not reinfection. It’s part of the recovery process ”, said Maria Van Kerkhove, technical manager at WHO, according to the BBC and AFP.
“It is not a reinfection”
What happened so that it was doubted for several weeks? “These patients were hospitalized and then cured after, generally, two negative virus tests, explains Anne-Claude Crémieux, infectious disease specialist at Saint-Louis hospital. But seen by a doctor two weeks later, some showed symptoms like fever, cough, headache. They were tested again with a nasopharyngeal swab and biologists found viral RNA “, says the specialist.
Is it a re-infection? Or did the erroneous outpatient screenings give “false negatives”? In the laboratory, biologists cultured the RNA fragments or “dead lung cells” found in all patients declared cured ” to better understand how long they harbor live virus ” and if they were contagious. Indeed, it is not because we find virus living in a patient’s respiratory tract that it is necessarily transmissible and contagious.
But the persistence of viruses being expelled
“ It seems that these patients are expelling viral material (ARN, Editor’s note), having persisted in the lungs, as part of the recovery phase “, explains WHO. “ Clearly, virologist biologists have confirmed the hypothesis of infectious disease clinicians: it is not a question of reinfection, but of persistence of viral debris during expulsion “, translates Anne-Claude Crémieux. Good news, because it exists with other viruses like measles for example. “Here, patients can clear viral debris for a long time, which is reassuring, because it does not go against the principle of immunity”, summarizes the infectiologist.
The heady question of the duration of immunity
However, with this coronavirus, Sras-CoV-2, two fundamental questions are still unanswered: what is the effective duration of protective immunity? And are patients who have had an asymptomatic form of the disease really protected?
Studies carried out in patients infected with Sras-Cov-1 in 2003 suggest that the majority of them develop adaptive immunity based on neutralizing antibodies for two or three years . But probably not for life.